Technically, you don't need Buldozer (O2 Viewer).
You can by all means just make your model in O2, save as P3D and check it in-game.
But, I would recommend that you d/l it. I did it before when I first got access to O2 (I'm a ModMaker). And I had 56k then.
IMO, it's worth the time d/ling it.
Cheers, KTottE